Multispectral Radiometric Analysis of Façades to Detect Pathologies from Active and Passive Remote Sensing

Abstract

This paper presents a radiometric study to recognize pathologies in façades of historical buildings by using two different remote sensing technologies covering part of the visible and very near infrared spectrum (530-905 nm). Building materials deteriorate over the years due to different extrinsic and intrinsic agents, so assessing these affections in a non-invasive way is crucial to help preserve them since in many cases they are valuable and some have been declared monuments of cultural interest. For the investigation, passive and active remote acquisition systems were applied operating at different wavelengths. A 6-band Mini-MCA multispectral camera (530-801 nm) and a FARO Focus3D terrestrial laser scanner (905 nm) were used with the dual purpose of detecting different materials and damages on building façades as well as determining which acquisition system and spectral range is more suitable for this kind of studies. The laser scan points were used as base to create orthoimages, the input of the two different classification processes performed. The set of all orthoimages from both sensors was classified under supervision. Furthermore, orthoimages from each individual sensor were automatically classified to compare results from each sensor with the reference supervised classification. Higher overall accuracy with the FARO Focus3D, 74.39%, was obtained with respect to the Mini MCA6, 66.04%. Finally, after applying the radiometric calibration, a minimum improvement of 24% in the image classification results was obtained in terms of overall accuracy.

The Effect of Building Facades on Outdoor Microclimate—Reflectance Recovery from Terrestrial Multispectral Images Using a Robust Empirical Line Method

“…Furthermore, the use of the EL method applied to terrestrial close-range MS sensors with near-horizontal viewing geometry of urban building facades has not been previously reported. However, there is growing interest in the use of ground-based, close range narrow FOV sensors for retrieval of the spatio-temporal optical and thermal characteristics of vertical surfaces at the facet and sub-facet scales for building damage assessment [148], geological surveys [85] and urban climatology [78].…”

Review of Methods for Documentation, Management, and Sustainability of Cultural Heritage. Case Study: Museum of King Jan III’s Palace at Wilanów

“…It includes radiometric calibration: The removal of fixed pattern noise (dark current), pixel sensitivity normalization, denoising, illumination correction, and finally spectral calibration to reflectance factor [83,121]. For low-cost imaging systems, additional corrections may also have to be applied, e.g., a vignette effect [122].…”

Geometric Analysis on Stone Façades with Terrestrial Laser Scanner Technology

“…In historic stone buildings, many different types of damage can occur including: loss of stone material, discoloration, deposits, detachment, fissures, deformation, and damage from previous intervention [1]. Detection of material degradation in historic buildings with traditional methods, such as manual mapping or simple eye examination by an expert [2], are considered time-consuming [3] and laborious procedures, so TLS (Terrestrial Laser Scanner) technology and image processing methodologies are being developed, allowing for the detection of pathologies [4,5], their evolution [6], identification of deformations [7], changes in material [8], and stone façade documentation [9][10][11].…”